The only cable-stayed bridge in Croatia, the Dubrovnik bridge, was opened for traffic in 2002. The main cable-stayed bridge with composite superstructure is jointed in span to the prestressed concrete approach bridge by a hinge-type connection. The bridge has experienced vibrations of cable stays under certain wind conditions, as with many other cable-stayed bridges around the world. After a short review of results of wind tunnel tests and various numerical analyses, field observations of cable-stay vibrations are highlighted. Only after extremely violent movements of cable stays and the superstructure under a heavy, damp snowstorm occurred, resulting in substantial damage, was it decided to apply vibration mitigation measures. Adjustable cable dampers, based on the latest MagnetoRheological (MR) technology, were installed on the bridge to raise low structural damping of the most affected cable stays.

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Over the last 20 years, beside their primary educational activities, members of the Bridge Chair of the Zagreb Faculty of Civil Engineering Structural Department also worked professionally on main and execution designs of many bridges. Most of them are mid-span to large span bridges, requiring detailed seismic design, especially since their locations are predominantly in highly seismic active regions. These bridges were designed during the transition period from old seismic standards, to ENV pre-standards, and finally to EC8 standards. The evolution of these codes had a great impact on the design. New demands in terms of seismic behaviour influenced all aspects of design, from conceptual design (structural system and material options), sizing of elements, foundation type, bearing and damper layouts, special equipment selection, erection details, to maintenance requirements. An overview of seismic design requirements, solutions, and peculiarities for each of these bridges, which were recently constructed or are currently under construction, is presented in the paper. Since the design of the cable stayed bridge Franjo Tuđman in Dubrovnik, where fluid viscous dampers were first employed in Croatia, to the recent bridge designs, various approaches were utilized to mitigate and take over the seismic actions. Adequate solutions were found either by structural detailing and/or by installation of seismic isolators, depending on bridge structural systems, utilized materials, but also on the characteristics of foundation soil.

The construction of a new 2.4 km long bridge, crossing the sea strait between the Croatian mainland and the Peljesˇac Peninsula to provide the fixed road link between the whole of Croatia, has just begun. The bridge location is in a highly seismic zone with the design ground acceleration of 0.41g and on extremely bad soil. The four-lane road bridge consists of two approach bridges and the main cable-stayed bridge with continuous steel trapezoidal box superstructure. Nonlinear modal time history analysis, based on superposition of Ritz vectors, but with coupled modal equations, was utilized for seismic design. Real earthquake accelerograms for earthquakes in the vicinity (Bar, Ulcinj, Ston) and also El Centro earthquake, as well as 72 artificial accelerograms, determined by seismic study for the specific bridge location, were analysed. The analysis was carried out taking into account the proposed construction sequence.